<!DOCTYPE html>
<html lang="ch">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let money=100
        while(true){
            let n =+prompt("1.存钱\n2.取钱\n3.查询余额\n4.退出\n")
            if(n===4){
                break
            }
        switch(n){
            case 1: 
            let cun=+prompt("存钱数额")
            money+=cun
            break  
            case 2: 
            let qu=+prompt("取钱数额")
            money-=qu
            break
            case 3: alert(`查询余额${money}`)
            break
        }
        }
       
    </script>
</body>
</html>